Ram-air turbines

ABSTRACT

A ram-air turbine comprises a variable-pitch bladed rotor, a hydraulic actuator for effecting pitch variation of the blading of the rotor, and a pump driven by the rotor to supply fluid for operation of the actuator. A rotary speed-sensitive flyweight governor is provided to control the supply of fluid to the actuator whereby to cause the rotor automatically to rotate at constant speed, and the arrangement includes a machine driven by the rotor. The rotor, hydraulic actuator, pump, governor and driven machine are all coaxially arranged.

United States Patent Chilman et al.

[451 ,lan..18,11972 [54] RAM-AIR TURBINES [72] Inventors: John Alfred Chilman, Painswick; Richard James Wall, Churchdown, both of England [73] Assignee: Dowty Rotol Limited, Gloucester, England [22] Filed: Nov. 7, 1969 [21] Appl. No.: 874,802

2,363,670 11/1944 Hoover ..416/48 1 2,379,302 6/1945 l-loover.... ....4l6/154 2,655,604 10/1953 l-lutter ..416/50 X 2,745,502 5/1956 Gehres ..416/157 2,986,219 5/1961 Boardman et aL ...416/48 3,080,928 3/1963 Godden et a1. ..416/46 3,125,960 3/1964 Chilman ..416/45 X 3,339,639 9/1967 Elmes et a1. ..416/48 Primary Examiner-Everette A..Powell, Jr. Attorney-Young & Thompson [5 7] ABSTRACT A ram-air turbine comprises a variable-pitch bladed rotor, a hydraulic actuator for effecting pitch variation of the hlading of the rotor, and a pump driven by the rotor to supply fluid for operation of the actuator. A rotary speed-sensitive flyweight governor is provided to control the supply of fluid to the actuator whereby to cause the rotor automatically to rotate at constant speed, and the arrangement includes a machine driven by the rotor. The rotor, hydraulic actuator, pump, governor and driven machine are all coaxially arranged.

10 Claims, 5 Drawing Figures PATENTEDMNI 81972 SHEET 1 UF 3 JNVENTORS' BY *JM ATTORNEYS PATENTEB JAN 1 8 1912 (16355 4 SHEET 3 or 3 da/m/ A; Flea-p Cw; MA fi e/ Aw 0/9/1453 144 244 INVENTORS ATTORNEYS RAM-AIR TURBINES This invention relates to ram-air turbines such as are used, for example, on aircraft to drive hydraulic, fuel or other pumps, electric generators or the like.

As used on manned aircraft, ram-air turbines usually constitute auxiliary power units to provide a lightweight and immediately available source of emergency power for the operation of hydraulic, electric or pneumatic services. Such auxiliary power units are sometimes mounted in a duct to which ram air is admitted by a scoop or other suitable means, or they may take the form of a dropout arrangement, for example being carried at the end of a leg by release of which the unit may be instantaneously moved from a position in which it is stowed within the aircraft out into the airstream so that the turbine will be immediately subject to the aerodynamic ram effect of the particular flight or takeoff conditions.

According to the invention a ram-air turbine comprises a variable-pitch bladed rotor, a hydraulic actuator for effecting pitch variation of the blading of the rotor, a pump driven by the rotor to supply fluid for operation of the actuator, a rotary speed-sensitive flyweight governor to control the supply of fluid to the actuator to cause the rotor automatically to rotate at constant speed and a machine driven by the rotor, said rotor, hydraulic actuator, pump, governor and driven machine all being coaxially arranged.

Preferably the hydraulic actuator, governor pump and driven machine are all coaxially arranged in tandem with each other. The pump supplying fluid for operation of the actuator may be sandwiched between the bladed rotor and the driven machine.

The governor may comprise a spool valve and speeder spring both disposed coaxially of the turbine rotor, the arrangement preferably being such that the spring puts the spool valve in position to bring the blades of the rotor to a substantially feathered position on stopping so that the blades are already in coarse pitchfor starting.

The hydraulic actuator preferably comprises a vane motor the casing vanes and shaft vanes of which are both angularly movable, one in a direction opposite to the other, about the axis of the bladed rotor in order to apply pitch-changing forces to the blades of the rotor at diametrically opposite points of the blades.

Thus, the vane motor casing and the shaft vanes are rotatable relatively to the hub of the rotor and may each carry a bevel gear, said bevel gears meshing with opposite points of bevel gears fast on the roots of the blades. Accordingly the bevel gears of the vane motor casing and of the shaft vanes apply turning moments to each blade in such manner that these moments are additive, journal loading at the blade roots being balanced. The construction thus avoids the setting up of friction-producing forces about the pitch-change axes of the blades during pitch change.

Preferably the vane motor casing carries at least three vanes while the shaft carries at least three vanes cooperating therewith. A thrust bearing may be provided between the vane motor casing and the bevel gear carried by the shaft vanes.

The pump supplying fluid for operation of the hydraulic actuator draws fluid from a reservoir which is preferably arranged externally of the ram-air turbine.

The spool valve is preferably of landed construction slidable linearly in a ported sleeve coaxial with the axis of rotation of the bladed rotor. Thus, the hydraulic actuator may have a hollow center and have the spool valve and sleeve disposed therewithin.

It will be understood that the datum of the speeder spring may be preset to enable the ram-air turbine to operate at a predetermined constant speed. Means for adjustment of the speeder spring may be positioned near a spinner structure of the rotor so as to be readily accessible. The ports in the sleeve open substantially directly into the hydraulic actuator for both pressure fluid supply to, and exhaust of fluid from, the actuator such substantially direct communication affording immediate operative response of the actuator to the demands of the spool valve. Each blade of the bladed rotor of the ram-air turbine is preferably provided with a balance weight fast upon the blade root adjacent to, and radially outwardly of, the bevel gear on the blade root but within the hub of the rotor.

One embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:

FIG. 1 is a partial axial section of a dropout ram-air turbine according to the invention,

FIG. 1A is a part of FIG. 1 to a larger scale, again in axial section,

FIGS. 2 and 3 are respectively cross sections on the lines ll-ll and III-III of FIG. 1A and FIG. 1, respectively, and

FIG. 4 is a diagrammatic layout drawing of the ram-air turbine of FIGS. 1 to 3 but illustrating a slightly modified hydraulic fluid circuit.

Referring to FIGS. 1 to 3 of the drawings, the ram-air turbine 10 includes a bladed rotor 11 mounted for rotation in antifriction bearings 12 and 13 carried in a body member 114. The body member is formed integrally with a leg 15 by which the turbine is pivotally mountable upon an aircraft structure in such manner as to be stowable within the aircraft. When the ram-air turbine is required to be brought into operation it is swung about the pivotal mounting of the leg into the airstream of the aircraft by suitable operating means (not shown).

The turbine is provided with two blades 16 which are each so mounted at their roots 17 in a plain journal bearing 18 and upon a roller thrust bearing 19 in the hub 20 as to be adjustable about their longitudinal axis X-X for variation in pitch. The hub 20 is of shell-like form having a nose or spinner por' tion 21 fitted upon a spigot 22 formed upon the forward end portion of the hub, to the left in FIG. 1A of the drawings. The rearward end portion of the hub is provided with a closure member 23 formed integrally with a hollow stepped shaft 24 which carries the inner races of the bearings 12 and 13.

A vane-type hydraulic actuator 25 is housed within the hub 20, its casing 26 being mounted with freedom both in the rotational and axial senses in a bore 27 formed in the spigot 22. As shown in FIG. 2, the casing has three inwardly directed vanes 28, 29 and 30, while the hollow shaft 31 of the actuator carries three radially outwardly directed vanes 32, 33 and 34. The vanes 32, 33 and 34 are formed integrally with a tubular portion 35 which is splined at 36 to the shaft 31. The rearward closure member 37 of the actuator is formed with a ring 38 of bevel gear teeth, the axis of rotation of the actuator, the axis of rotation of the ring 38 and the axis of rotation of the bladed rotor all being coincident, as shown at Y. The teeth of the bevel gear ring 38 are in mesh with two bevel gears 39 and 40 respectively splined upon the root portions of the two blades 16. Balance weights 41 and 42 are also splined to the blade root portions immediately adjacent the bevel gears 39 and 40 on the radially outer side thereof.

Towards its rearward end portion (to the right in FIG. 1A) the shaft 31 is provided with splines 43 upon which is fitted a bevel gear 44 locked in the axial sense upon the shaft by a ring nut 45. The bevel gear 44 meshes with the two bevel gears 39 and 40. The components of the actuator casing 26, the vanes 28, 29 and 30 and a thrust ring 46 which extends rearwardly from and coaxially with respect to the casing are held in assembly by three longitudinally extending set bolts, one of which is shown at 47 in FIG. 1A. The forward race 48 of a roller thrust bearing 49 seats in the base of a counterbored portion 50 of the thrust ring 46. This race also bears against a shoulder 51 formed upon the shaft 31. A screw-threaded ring 52 fits into the thrust ring 46 and retains the rollers 53 and rearward race 54 of the thrust bearing 49 in operative assembled condition with the forward race 48.

The rearward end portion of the shaft 31 projects into the hollow stepped shaft 24 of the closure member 23 and there carries longitudinally extending projections 55 and 56 having pivots 57 and 58 upon which speed-sensitive governor flyweights, one of which is shown at 59, are fitted. The tails 60 of both flyweights engage a hollow landed valve spool 61 whose axis is coincident with the rotational axis of the bladed rotor. The spool is linearly displaceable in a ported sleeve 62 locked in the axial and rotational senses to the hollow interior ofthe shaft 31.

A governor speeder spring 63 is provided within the sleeve 62 bearing at its rearward end portion upon the forward end portion of the spool 61. The spring bears at its forward end portion upon shims 64 carried by a plug member 65 which screws into the forward end portion of the sleeve. Around its periphery, and as shown in FIG. 2, the sleeve 62 is provided with six axially directed grooves 66, 67, 68, 69, 70 and 71. A radial port 72 is provided in the spool, placing its hollow interior in communication with an annulus 73 formed between two spool lands 74 and 75. When the spool is in its equilibrium position, as shown in FIG. 1A, these lands close over the radial ports 76 and 77 formed in the sleeve 62. Further annuli 78 and 79 formed in the spool align with radial ports 80 and 81 in the sleeve 62.

The ports 76 open to the grooves 66 and 69 which in turn open through ports 82 and 83 in the shaft 31 and ports 84, 85, 86 into fine pitch chambers 87, 88, 89 of the actuator. The ports 77 open to the grooves 68 and 70 which in turn open through ports 90 into the shaft 31 and ports 91, 92, 93 into coarse pitch chambers 94, 95, 96 of the actuator. The ports 80 and 81 open to the grooves 67 and 71 in the sleeve 62 which are themselves indirect communication with drain.

The blades16, hub 20, actuator 25, sleeve 62, governor flyweights 59, spool 61 and shaft 24 are all rotatable as one with respect to the body member 14. The shaft 24 is splined at 97 to a hollow quill shaft 98 which projects through a closure plate 99. The rearward portion of the shaft 98 is splined at 100 and connected to drive a hydraulic pump 101 mounted upon the body member. The rotatable part 102 of an internally meshing lobe-type pump 103 is mounted upon the quill shaft 98 and has a splined connection 104 to the rearward extremity of the shaft 24. A passageway 105 is provided in the leg 15 and is open through registering passageways 106 and 107 in the body member 14 and the closure plate 99 to the inlet of the lobe-type pump 103. Delivery from this pump, which is intended for operation of the vane-type actuator 25 for pitchchange, occurs through a passageway 108 in the rotatable part 102 which opens through radial ports 109 in the quill shaft 98 into the interior of the latter. The hollow interior of the quill shaft is in open communication with the hollow interior of the valve spool 61.

At its rearward end portion the interior of the quill shaft 98 is provided with a pressure relief valve 110 which, when operative, discharges to the inlet side of the pump 103. As shown in FIG. 3, a connection 111 is taken from the passageway 105 and this connects through suitable piping (not shown) to the inlet of the pump 101. Furthermore piping leads from the delivery connection of the pump 10] to another connection 112 on the leg 15. This connection is in communication through a cross-channel 113 with a passageway 114 running back through the leg 15 to equipment within the aircraft which utilizes the delivery of the pump 101. The body member 14 of the ram-air turbine 10 is suitably sealed, its bearings 12 and 13 being flood-lubricated. A carbon sealing ring 1 15 is provided in the body member.

When it is required to bring the ram-air turbine 10 into operation, the leg 15 is swung about its pivotal mounting upon the aircraft so that the unit is moved into the aircraft airstream. It is so arranged that the blades 16 are at a relatively coarse pitch angle suitable for starting under the effect of the airstream, yet without stalling. The angle is such that although providing best starting torque, the free rotational speed of the rotor is limited to a safe value so that should the pitch-change mechanism fail to operate correctly rotor overspeeding cannot occur.

Hydraulic fluid derived from the aircraft hydraulic system at a base pressure of 20 pounds per square inch passes through the passageway l'and connection 111 to the inlet of the pump and through the passageways 106 and 107 to the inlet of the pump 103. The pump 101 then commences to deliver liquid under pressure through the connection 112, cross-channel 113 and passageway 114 into the equipment requiring it within the aircraft. The pump 103 delivers liquid under pressure through the passageway 108 into the interior of the quill shaft 98 and thence into the interior of the spool 61, passing through the port 72 into the annulus 73.

Upon starting, the turbine is running at a relatively low speed with the blades at a correspondingly coarse pitch angle. Thus, the governor flyweights 59 are overpowered by the effect of the speeder spring 63. Hence the spool 61 is urged rearwardly so that the annulus 73 is open to the fine pitch ports 76. At the same time the coarse pitch ports 77 are open to the annulus 79 which in turn is open to the ports 81 and drain groove 71. The groove 71 is then in communication with the interior of the body member 14 in which the liquid pressure is maintained at 20 pounds per square inch by the base pressure supply. Liquid under pressure passes from the ports 76 through the grooves 66 and 69 in the sleeve 62, ports 82 and 83 in the shaft 31, and ports 84, 85, 86 into the three fine pitch chambers 87, 88 and 89 of the actuator 25. At the same time the coarse pitch chambers 94, 95 and 96 of the actuator are placed in communication with drain through the ports 91, 92 and 93, ports in the shaft 31, grooves 68 and 70 in the sleeve 62, ports 77 also in the sleeve 62, annulus 79 in the spool 61, ports 81 and the grooves 67 and 71.

Since the casing 26 of the actuator 25 is free to rotate in the spigot 22, and since the bevel gear 38 of the casing and the bevel gear 44 on the shaft mesh with the two bevel gears 39 and 40 on opposite sides thereof respectively, then as the fine pitch chambers of the actuator increase in volume, the casing 26 moves angularly about the actuator axis in one direction while the output shaft 31 moves angularly in the opposite direction. Such movements are equal and by virtue of the three-vane construction occur relatively smoothly. The moments applied by the casing and shaft to the respective gears 39, 40 are additive but the thrusts are so substantially balanced on either side of the pitch-change axis X of the respective blade that substantially no journal loading at the blade roots is created by the pitch-changing function.

' The pitch-changing of the blades continues in the pitch-fining direction until the rotational speed of the ram-air turbine reaches a value predetermined by the datum setting of the speeder spring 63. As this speed is reached flyweights 59 have moved radially outwardly about their pivots 57 and 58 to a position in which the valve spool 61 is displaced against the speeder spring sufficiently far for the lands 74 and 75 to close over the ports 77 and 76, as shown in FIG. 1A, so that the spool is in its equilibrium setting at the on-speed condition. Hence the vane actuator 25 ceases to move further and the pitch is maintained at the required value. During operation, the balance weights 41 and 42 at the blade roots oppose the pitch-fining effect of the inherent centrifugal twisting moments of the blades 16 in conventional manner. Also the thrust bearing 49 at all times resists axial separation of the bevel gears 38 and 44 from their meshing condition with the bevel gears 39 and 40. The gear ratio in the bevel gear drive for blade pitch-change is in this embodiment 2.2:1 step up.

If during operation of the ram-air turbine the rotational speed of the bladed rotor 11 commences to increase due to increased speed of the aircraft or some other aerodynamic condition, the governor fly-weights 59 are immediately responsive to this change and move radially outwardly about their pivots 57 and 58. The valve spool 61 thus moves forwardly in the sleeve 62 away from the equilibrium position and against the effort of the speeder spring 63. Such movement places the annulus 73 in communication with the coarse pitch ports 77, and thus liquid under pressure passes through the grooves 68 and 70 in the sleeve 62, through the ports 90 in the shaft 31 and through the ports 91, 92, 93 in the tubular portion 35. Thus the coarse pitch chambers 94, and 96 of the actuator 25 are caused to increase in volume, the liquid exhausting from the fine pitch chambers 87, 88 and 89 passing through the ports 84, 85 and 86 in the tubular portion 35, ports 82 and 83 in the shaft 31, grooves 66 and 69 in the sleeve 62, ports 76 also in the sleeve 62, annulus 78 in the spool 61, ports in the sleeve 62 and through grooves 67 and 71 to drain.

Thus, again, in view of the freedom of movement of the casing 26 of the actuator 25 with respect to the hub 20, the casing moves in one direction about the rotational axis Y of the actuator while the shaft 31 moves by an equal amount in the opposite direction, the moments applied to the bevel gears 39 and 40 fixed to the blade roots being additive while the journal loading upon the blade roots is balanced. The pitch of the blades 16 is thus coarsened so that the rotational speed of the rotor 11 commences to fall. As the speed falls to the required datum setting the governor flyweights 59, being sensitive to the speed condition, allow the valve spool 61 to move back to its equilibrium position under the control of the speeder spring 63, whereupon further pitch-change movement under the power of the actuator 25 ceases.

If during operation of the ram-air turbine the rotational speed of the bladed rotor falls below the required datum setting, the governor flyweights 59 are responsive to allow the valve spool 61 to move rearwardly of the hub, so that in converse manner the actuator operates to appropriately reduce the pitch of the blades for reattainment of the required datum setting.

When the bladed rotor 11 is in its on-speed condition, the delivery of the pump 103 passes through the relief valve 110 back to the inlet of the pump.

If it is desired to adjust the datum setting of the governor, then when the aircraft is on the ground with the ram-air turbine inoperative, the spinner portion 21 is removed from the spigot 22 and the plug member 65 is unscrewed from the interior of the sleeve 62. The shims 64 are then increased or reduced in number as the case may be and the plug member 65 and spinner portion 21 refitted. In this way the adjustment is relatively easily achieved and does not require major stripping of the components.

Referring to FIG. 4, in the modified hydraulic fluid circuit illustrated therein a branch line 116 is tapped from the passageway 105 carrying hydraulic fluid at the aforesaid base pressure to the pump 101, such branch line supplying the pump 103 of the pitch control system, including the valve and governor assembly which is shown as a coritrol block 120, of the ram-air turbine 10. The return line 117 from this system reconnects with the input line to the pump 101 formed by the passageway 105 at a point downstream of the tapping 116. Hence, heat generated in the pitch control system is carried through the pump 101 and into the pump delivery line constituted by the passageway 114 to the aircraft system. Accordingly the pitch control system continuously rejects its heat to the aircraft system and thus avoids an internal heatregenerative cycle.

The invention as applied in the described embodiment provides a ram-air turbine in which pitch-change of the blades is effected automatically by the operation of an actuator, the casing of which is free to move with respect to the hub of the rotor, the pitch-changing force exerted by the casing being applied to each blade at a position with respect to its pitchchange axis diametrically opposite to the position at which the pitch changing force exerted by the output member of the actuator is applied.

Thus, the actuator applies turning moments to each blade which are additive, but journal loading at the blade roots is substantially balanced. The construction thus avoids the cessories may be fitted, for example electric alternators.

We claim:

1. A ram-air turbine comprising a variable-pitch bladed rotor, a hydraulic actuator for effecting pitch variation of the blading of the rotor, a pump driven by the rotor to supply fluid for operation of the actuator, a rotary speed-sensitive flyweight governor associated with a hydraulic valve for controlling the supply of fluid to the actuator to cause the rotor automatically to rotate at constant speed and a machine driven by the rotor, said rotor, hydraulic actuator, pump, governor and driven machine all being coaxially arranged with the governor and valve housed within the rotor and the rotor, pump and machine being connected together by coupling means whose axis is coincident with the common rotational axis of these components.

2. A ram-air turbine according to claim 1, wherein the hydraulic actuator, governor, pump and driven machine are all coaxially arranged in tandem with each other.

3. A ram-air turbine according to ciaim 2, wherein the pump supplying fluid for operation of the actuator is sandwiched between the bladed rotor and the driven machine.

4. A ram-air turbine according to claim ll, wherein the governor comprises a spool valve and speeder spring both disposed coaxially of the turbine rotor.

5. A ram-air turbine according to claim 41, wherein the arrangement is such that the spring puts the spool valve in position to bring the blades of the rotor to a substantially feathered position on stopping so that the blades are already in coarse pitch for starting.

6. A ram-air turbine according to claim 4, wherein the hydraulic actuator has a hollow center within which the spool valve is disposed, and wherein respective ports of the valve open substantially directly into the hydraulic actuator for both pressure fluid supply to, and exhaust of fluid from, the actuator.

7. A ram-air turbine according to claim 1, wherein the hydraulic actuator comprises a vane motor the casing vanes and shaft vanes of which are both angularly movable, one in a direction opposite to the other, about the axis of the bladed rotor in order to apply pitch-changing forces to the blades of the rotor at diametrically opposite points of the blades.

8. A ram-air turbine according to claim 7, wherein the vane motor casing carries at least three vanes while the shaft carries at least three vanes cooperating therewith.

9. A ram-air turbine according to claim 7, wherein the casing and shaft vanes of the motor each carry a corresponding one of two bevel gears which mesh with opposite points of further bevel gears fast on the roots of the blades.

10. A ram-air turbine according to claim 1, wherein the pump supplying fluid for operation of the actuator discharges through a relief valve which maintains a minimum actuator operating pressure, conduit means being provided whereby the fluid discharging from the relief valve is carried away from the turbine to avoid an internal heat-regenerative cycle. 

1. A ram-air turbine comprising a variable-pitch bladed rotor, a hydraulic actuator for effecting pitch variation of the blading of the rotor, a pump driven by the rotor to supply fluid for operation of the actuator, a rotary speed-sensitive flyweight governor associated with a hydraulic valve for controlling the supply of fluid to the actuator to cause the rotor automatically to rotate at constant speed and a machine driven by the rotor, said rotor, hydraulic actuator, pump, governor and driven machine all being coaxially arranged with the governor and valve housed within the rotor and the rotor, pump and machine being connected together by coupling means whose axis is coincident with the common rotational axis of these components.
 2. A ram-air turbine according to claim 1, wherein the hydraulic actuator, governor, pump and driven machine are all coaxially arranged in tandem with each other.
 3. A ram-air turbine according to claim 2, wherein the pump supplying fluid for operation of the actuator is sandwiched between the bladed rotor and the driven machine.
 4. A ram-air turbine according to claim 1, wherein the governor comprises a spool valve and speeder spring both disposed coaxially of the turbine rotor.
 5. A ram-air turbine according to claim 4, wherein the arrangement is such that the spring puts the spool valve in position to bring the blades of the rotor to a substantially feathered position on stopping so that the blades are already in coarse pitch for starting.
 6. A ram-air turbine according to claim 4, wherein the hydraulic actuator has a hollow center within which the spool valve is disposed, and wherein respective ports of the valve open substantially directly into the hydraulic actuator for both pressure fluid supply to, and exhaust of fluid from, the actuator.
 7. A ram-air turbine according to claim 1, wherein the hydraulic actuator comprises a vane motor the casing vanes and shaft vanes of which are both angularly movable, one in a direction opposite to the other, about the axis of the bladed rotor in order to apply pitch-changing forces to the blades of the rotor at diametrically opposite points of the blades.
 8. A ram-air turbine according to claim 7, wherein the vane motor casing carries at least three vanes while the shaft carries at least three vanes cooperating therewith.
 9. A ram-air turbine according to claim 7, wherein the casing and shaft vanes of the motor each carry a corresponding one of two bevel gears which mesh with opposite points of further bevel gears fast on the roots of the blades.
 10. A ram-air turbine according to claim 1, wherein the pump supplying fluid for operation of the actuator discharges through a relief valve which maintains a minimum actuator operating pressure, conduit means being provided whereby the fluid discharging from the relief valve is carried away from the turbine to avoid an internal heat-regenerative cycle. 